Nature’s Cutest Symbiosis: The Bobtail Squid | I Contain Multitudes

Nature’s Cutest Symbiosis: The Bobtail Squid | I Contain Multitudes

[MUSIC PLAYING] Hello. Yes, it’s me, right here. Being able to turn invisible,
or at the very least being incredibly
well-camouflaged, is incredibly useful,
especially if I was a spy. I’m not a spy. For me, it would be really
fun to be able to disappear from view on a whim. But for this creature,
being able to disappear is a matter of life and death. This is the Hawaiian
bobtail squid. It’s no bigger than a walnut,
but it’s full of personality. I’m rather taken by it. I think it’s
spectacularly beautiful. But for many of the
creatures in the ocean, the squid could best be
described as delicious. So the squid has evolved
a host of strategies to hide from hungry predators. It can cover itself with sand. It can change its color to
blend into its surroundings. It can eject an ink blob
to cover its escape. But at night, it has to head up
into the water column to hunt. And here, it is
especially vulnerable. So it uses an amazing trick. It can disappear by glowing. If you look at the little
creature’s underside, you see a pair of structures
called the light organ. These project light shining
down below the animal, which matches the moonlight
and starlight whirling down from above. So any predator looking
up at the squid from below can’t make out its silhouette. This behavior is called
counter-illumination. And it’s quite handy if you’re
trying to avoid being eaten. They’re very tasty. That’s Margaret McFall-Ngai,
a zoologist at the University of Hawaii. I’ve actually never had a
bobtail squid from Hawaii. But I have had a bobtail
squid in the Mediterranean. And when she’s
not occasionally snacking on bobtail squid,
she’s studying them. She finds them fascinating
because these animals can’t actually produce any
light on their own, not a single photon. Instead, the light comes
from Vibrio fischeri, a bacterium that lives
inside the light organ. Without these bacteria– MARGARET MCFALL-NGAI:
The animal would be picked off by a predator. But what do the
bacteria get out of it? They get a supply of food. And they’re not out in the
water with the potential of some protozoan coming
along and eating them. That’s Ned Ruby. He is Margaret’s partner,
in work and in life. He focuses on the
bacterium, while she concentrates on the squid. [INAUDIBLE]. ED YONG: And the
two of them, much like the creatures they
study, live in what could best be described as a symbiosis. Very simply, from the
Greek “symbiosis,” which is– The living together of
two dissimilar organisms. –to live together– Persistent living together. –for long periods
of their lifetime. They’ve been working
together for around 30 years. And in that time,
they have turned the squid and its bacteria
into icons of symbiosis. The bobtail squid is
a great study subject because it’s just one
bacterium and one host animal. And the squid is born
without its microbial buddy, allowing Margaret and Ned to
conduct a simple but powerful experiment. They raised two sets
of bobtail squid, one with their symbiotic
bacteria and one without. And then they compared the two. And what did you find
when you raised the squid without their bacteria? The animal was perfectly
happy and healthy– Except– Except? MARGARET MCFALL-NGAI: In the
absence of Vibrio fischeri, they don’t develop light
organs and don’t make light. Huh. So the squid need
Vibrio fischeri in order to develop the light organ? Exactly, Ed. When the juvenile squid is
born, there is a structure. This nascent light
organ, we call it, because it hasn’t yet
begun to produce light. MARGARET MCFALL-NGAI:
Once the bacteria get in, they say to the
animal, I’m here. I’m going to direct you in the
sculpting of that structure. NED RUBY: Into
this very complex, multi-tissue structure– MARGARET MCFALL-NGAI:
–that will function in counter-illumination
effectively. This is a profound discovery. It means that microbes help
to sculpt some animal bodies. Yes. That’s exactly what happens. If you watch a fertilized egg
under a microscope, a human, squid– any will do– you’ll see it divide into two,
and then four, and then eight. It folds, bulges, and contorts. Body parts start to form. An embryo grows. This whole sequence
seems self-contained, barreling along like a
complicated computer program. But the squid tells us that
development in many animals is not always a monologue. It can be a conversation
between different species. The squid, for
example, is surrounded by countless species of microbes
floating out in the open ocean. But somehow, it only
lets Vibrio fischeri into the juvenile light organ. And Margaret and Ned
have shown exactly how this exclusivity works. MARGARET MCFALL-NGAI:
One of the things that the juvenile light organ
has that the adult light organ does not have is a set
of appendages on its surface. And on those appendages
are very, very active cilia, which are like hairs. ED YONG: The hairs
create currents that draw in particles of
bacterial size and no bigger. MARGARET MCFALL-NGAI: That’s
when chemistry comes in. The animal has put
into the environment a bunch of molecules,
a cocktail to which only Vibrio fischeri
seems to be able to adapt. NED RUBY: When the
bacterium comes in contact with the tissues
of the squid, it’s getting some signals
that tell it where to go, where to enter
this animal’s body. MARGARET MCFALL-NGAI:
They go up a long duct, into an antechamber. And then, on average,
a single microbe squeezes through a
bottleneck on the other side of the antechamber. NED RUBY: The bacteria
begin to grow up into hundreds of
thousands of cells. MARGARET MCFALL-NGAI: And
they signal to the host, you can go on to
mature the light organ. The light organ changes shape. It changes chemistry. It needs to develop other
tissues around the outside of this organ. Like an iris, so it can adjust
its brightness and fine-tune its camouflage. That is how the
light organ forms. And having been colonized
by the right bacteria, it won’t be colonized again. These partners are
now set for life. It’s become clear that many
animals, from fish to mice, rely on microbes to
build their bodies. And it seems likely
that we humans also grow up under the influence
of our microbial partners. I’m an animal biologist. I would love to be able to say
that the microbial world is not at the center of everything. But it is. So which bacteria do
I need to host in order to become invisible? Margaret? MARGARET MCFALL-NGAI:
Goodbye, Ed. NED RUBY: Goodbye, Ed. The bobtail squid is
far from the only animal with microbial superpowers. And some of the
others are featured in our “Microbe Minute.” For example, the pufferfish
uses a neurotoxin made by microbes to defend
itself against predators. If you know about other cool
animal-microbe interactions, let me know in the comments.

19 thoughts on “Nature’s Cutest Symbiosis: The Bobtail Squid | I Contain Multitudes

  1. Eye see you. And a question, is the thing from the tv show limitless, the man-made organism that ate electricity possible?

  2. Great video !
    How does the body know if there are enough bacterias to mature the light organ?
    Do the bacterias act as ligand and then active genes?

  3. I wonder if the initial shaping process used to be handled by inner biological processes; and if so weather the inner process was out-competed by the bacteria or it was lost (due to mutation/degradation/etc) and replaced. 🤔Probably the latter, since it's less likely and that's how nature seems to work.

  4. So interesting! I would love to see some of the sources used in this video so I can read up on the subject. Especially the formation of the light organ.

  5. Cute little critters. Check out an extremely venomous little cousin of theirs that lives 'round Australian waters: The Blue Ringed Octopus . I wonder just what lives inside those bright blue rings..?

    ~ ~ ~

    Isn't there evidence that childhood exposure (among humans) to certain bacteria helps to program our immune cells (specifically the 'B' type cells)?

    There's even a theory (the Hygiene Hypothesis) that the massive increase of autoimmune diseases in humans is the result of our dedicated work (over the past few centuries) to eradicate many of these parasites (especially Helminths), bacteria & other microorganisms (either attacking them directly with vaccines, or by improving the hygiene of our environments) that we've been at war with for millions of years (as a homonid species, anyway).

    By having such a 'clean' environment throughout our childhood years, we've inadvertently miscalibrated part of our immune systems (possibly the Thymus gland), leading to an immune response that works excessively & also has difficulty telling friend from foe (attacking our own cells).

    I'd certainly like to hear your opinions about this fascinating theory.

  6. Ed Yong this is not Darwinian Evolution. I think this is Margulian Evolution in honor to
    the scientific Lynn Margulis,she proposed that symbiosis is an important mechanism in evolution.
    Greetings from Nuevo Laredo Tamaulipas Mexico ¿Do you speak spanish?

  7. Something quite interesting regarding this research is that the main factor related to the development of the squid's light organ is the monomer of V. fischeri's peptidoglycan (PGN), tracheal cytotoxin (TCT). Besidesthe PGN and lipopolysaccharides (LPS), TCT by itself induces the three main factors that initiates the development of the light organ: hemocytes infiltration (immune system cells, mainly released when there is an infection), apoptosis (programmed cell death, but in this case is induced by TCT) and regression of epithelial fields (process in which the epithelial cells in the light organ, in these called “fields” are returned to a less developed state). All these factors are accounted for the development of such light organ, which the squid uses for camouflage and evade predators.
    These factors, personally, seem quite invasive… if not pathogenic.
    TCT is known to play an important factor in whooping cough and gonorrhea, which is mentioned in Koropatnick et. al., 2004. I'm merely a undergraduate student, and I'm sure if any microbiologist or even Ed can prove me wrong at my point; but being induced apoptosis from TCT one of the factors for the light organ's development… is this development through adaption of what could be a pathogenic reaction towards this specific signal? I'm sure there are many other species that see benefit from this kind of interaction, in which they are induced a signal which in one's perspective can be damaging for their cells but that specie still uses it for its development, which is fascinating.
    mentioned on his/her comment that is "Margulian Evolution in honor to

    the scientific Lynn Margulis, she proposed that symbiosis is an important mechanism in evolution." which in my perspective would make sense, I'll have to look closer at Margulis' theory for this analysis.
    Maybe the reason the Ed didn't mention TCT was because it is signaling this pathogenic-like behaviors towards its hosts; and the host is, as mutualism describes, benefited from this interaction in which it develops its light organ for the desired function. Yes, there is mutualism involved, but raises from the pathogenic behavior of V. fischeri towards its host and its epithelial cells.

    In my humble, undergraduate-level perspective is something that needs to be further analyzed to comprehend the role of TCT in this situation and in other situations it is involved in as well

  8. WOW astounding ! it's incomprehensible to me how anything so microscopic can be observed over a long enough period of time for a scientist to explain how it works. I'm speechless. Note: evolution could never account for such creativity, only a Creator can do that 🙂

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